The present invention relates to a semiconductor device and a method for manufacturing the same, more specifically, a semiconductor device including capacitors and a method for manufacturing the same.
Recently, it is noted to use a ferroelectric film as the dielectric film of capacitors. A FeRAM (Ferroelectric Random Access Memory) using such ferroelectric capacitors is a nonvolatile memory having characteristics of high-speed operation, low power consumption, and good endurance of write/read operation, etc. FeRAM is expected to develop more.
In addition to FeRAM, it is proposed that a ferroelectric film or a high dielectric film be used for the dielectric film of DRAM capacitors for higher integration.
A proposed semiconductor device is explained with reference to FIG. 1. FIG. 1 is a cross-section diagram of the proposed semiconductor device.
As illustrated in FIG. 1, conductor plugs 146 are buried in an inter-layer insulation film 140. An adhesion layer 148 of, e.g., TiN is formed on the conductor plugs 146 and the inter-layer insulation film 140. An oxygen barrier film 150 of, e.g., TiAlN is formed on the adhesion layer 148. The oxygen barrier film 150 is for preventing the surfaces of the conductor plugs 146 from being oxidized. Lower electrodes 156 are formed on the oxygen barrier film 150. A capacitor dielectric film 162 of a ferroelectric or high dielectric is formed on the lower electrodes 156. Upper electrodes 170 are formed on the capacitor dielectric film 162. The lower electrodes 156, the capacitor dielectric film 162 and the upper electrodes 170 form capacitors 172.
The use of Pt as a material of the lower electrodes 156 is proposed. On the lower electrodes 156 of Pt, the capacitor dielectric film 162 of good crystallinity can be formed.
However, when the lower electrodes 156 are formed of Pt, the Pb or Bi contained in the capacitor dielectric film 162 passes through the lower electrodes 156 and arrives at the oxygen barrier film 150, because a Pt film does not have a function of barriering Pb or Bi. When the Pb or Bi contained in the capacitor dielectric film 162 arrives at the oxygen barrier film 150, the oxygen barrier film 150 reacts with the Pb or Bi, and the adhesion between the oxygen barrier film 150 and the lower electrodes 156 is impaired. Then, as shown in FIG. 2, the lower electrodes 156 are released from the oxygen barrier film 150, and the semiconductor device cannot have high reliability. FIG. 2 is a view of a microscopic picture of the lower electrodes released from the barrier film.
FIG. 2 was obtained by using an SEM (Scanning Electron Microscopy). Thus, when the lower electrodes 156 are formed of Pt, the lower electrodes 156 are released from the oxygen barrier film 150, and the semiconductor device cannot have capacitors of high reliability.
On the other hand, the use of Ir as a material of the lower electrodes 156 is proposed. Ir film, which has the function of barriering Pb or Bi, can prevent the arrival of the Pb or Bi contained in the capacitor dielectric film 162 at the oxygen barrier film 150 and can prevent the release of the lower electrodes 156 from the oxygen barrier film 150.
However, when the lower electrodes are formed of Ir film, it is difficult for the capacitor dielectric film can have good crystallinity.